DESCRIPTION: (Applicant's Description) The objective is to establish a registry of families with multiple cases of colorectal cancer. Specific aims are: 1) Contact cases of colorectal cancer in participating population-based cancer registries and identify cases with a positive family history of colorectal cancer. The applicant proposes to contact 50 percent of White cases diagnosed in 1996/97 (2-year period). The applicant also proposes contacting 100 percent of African-American, Asian, and Hispanic families and cases diagnosed under 50 years of age for a period of four years. Over 1,200 families with two cases of colorectal cancer and about 400 with at least three cases of colorectal cancer will be identified. 2) Supplement this population-based series of families with a large registry of 382 families with FAP (3,250 subjects) and 100 (Amsterdam criteria) HNPCC families (900 subjects) and 250 HNPCC-like families (2,250 subjects) identified by the Cleveland Clinic. 3) For families identified from the population-based registries, maintain a file with contact information on 10 percent of sporadic cases and all families with two cases of colorectal cancer (due to cost constraints, additional data collection for these families is not proposed at this time). For families with three or more cases of colorectal cancer, the applicant proposes to use a case-unaffected sibling or cousin control design to define subjects on whom to collect additional data, including: a) food frequency questionnaire, with a supplement to obtain additional information on exposure to heterocyclic amines by computer assisted telephone interviews (CATI); b) a risk factor questionnaire that will focus on physical activity, NSAIDs, smoking, alcohol, and hormones, obtained by CATI; c) blood sample; d) for cases of colorectal cancer (and other cancers of interest), pathology reports and tumor blocks. 4) For families in the FAP/HNPCC registry at the Cleveland Clinic, collect additional data as described above for cases, unaffected siblings and cousins, and other selected relatives. 5) Develop a highly efficient system for managing these data. 6) Provide genetic counseling services. 7) Collaborate with the other centers of the CFRCCS. An important aspect of this application is that all investigators have agreed in principle that the study design may be amended and priorities shifted (e.g., targeting certain subgroups defined by age, race or other variables) and budgets revised accordingly in response to decisions made by the CFRCCS.